Diversity of opportunistic black fungi on babassu coconut shells, a rich source of esters and hydrocarbons

The present study assessed the diversity of black yeast-like fungi present on babassu coconut shells, a substrate rich in lipids and several volatile organic compounds (VOCs) including aromatic hydrocarbons. Using different isolation methods, one-hundred-six isolates were obtained and were identified by ITS sequencing as members of the genera Exophiala, Cladophialophora, Veronaea, and Rhinocladiella. Two novel species were discovered. Eight strains were selected for assessing their ability to grow on toluene and phenyl acetate as the sole carbon and energy source. All strains tested were able to assimilate phenyl acetate, while two out of eight were able to use toluene. VOCs profiling in babassu samples was also investigated by GC-ToF MS, revealing that a complex mixture of VOCs was emitted, which included alkylbenzenes such as toluene. Assimilation of alkylbenzenes by the black yeasts might therefore be the result of evolutionary adaptation to symbiotic interactions with higher plants. The potential relationship between lipid/aromatic hydrocarbon metabolism and pathogenicity is also discussed.